Clip art illustrates virtually every medium in the modern graphic arts. Whether paid or free, clip art has become the stock in trade of both amateur and professional desktop publishing. Originally, clip art received its name from the production process. Design teams would build scale models of a given layout as a "paste up"-that is, a larger version of the layout that would eventually be printed. The team photographed the paste up and used the negative to create the actual printing plate; however, previous to this, the paste up needed some pasting up. That is where the clip art came in.
Whatever baby clip art you decide to use, be sure to keep a common theme throughout all of your projects. For instance, having matching thank you notes is a nice compliment to your invitations. Also, having personalized stationery for the mother to write her own personal thank you notes would be a wonderful idea.
Inkscape is also widely used by a lot of people, many of whom have created tutorials showing you how to use the software, and that makes it even easier to download a piece of vector clip art and use it in your project.